This invention relates to an electrolytic cell and in particular a cell with improved electrolyte flow distributor.
It is well established that various chemicals can be produced in an electrolytic cell containing an anode and a cathode. For example, alkali metal bromates and chlorates, such as sodium chlorate, have been formed electrolytically from a sodium chloride brine in cells without a separator positioned between the anode and cathode. When a separator, such as a liquid permeable asbestos or polytetrafluoroethylene diaphragm or a substantially liquid impervious ion exchange membrane, is used in a cell to electrolyze a sodium chloride brine, the electrolytic products will normally be gaseous chlorine, hydrogen gas and an aqueous solution containing sodium hydroxide.
For a number of years, gaseous chlorine was produced in electrolytic cells with an asbestos diaphragm interposed between finger like anodes and cathodes which were interleaved together. During the past several years, it has become apparent that the use of a substantially liquid impermeable cation exchange membrane may be preferable to the well established diaphragm in instances where a higher purity (for example, a lower sodium chloride content) sodium hydroxide product is desired. It was found to be more convenient to fabricate ion exchange type electrolytic cells from relatively flat or planar type electrolytic cells from relatively flat or planar sheets of ion exchange membrane rather than to interweave the membrane between the anode and cathode in the older finger like or battery leaf type cells having asbestos diaphragms.
The newer, so called flat plate electrolytic cells using a planar sheet of ion exchange membrane have allowed the industry to develop much larger and substantially thinner electrolytic cells than its predecessor electrolytic cell design previously described. The increase in size is relative, namely an increase in size in two dimensions while holding the depth of the structure relatively thin.
The conventional operating mode of large size flat plate electrolytic cells is to provide a direct current causing ionic transfer across the membrane, the current flowing between spaced anode and cathode electrodes. Adjacent cells are separated by a plurality of liquid impervious frames adapted to support the anode on one side and the cathode on the opposite side. In conjunction with the development of relatively thin flat plate electrolytic cells, membranes have also improved. Membranes are now available to the industry that operate at substantially higher current loads, thereby yielding a substantial increase in production. With this substantial increase in production, a problem of providing an increased flow of liquids into and gas and liquid flow out of this type of cell has become a major concern. Typically, these inlet and outlet lines have been fabricated using circular piping designs.
The above features of a flat plate bipolar electrode type, filter press type electrolytic cell unit can also be observed in the following references: U.S. Pat. Nos. 4,364,815; 4,111,779; 4,115,236; 4,017,375; 3,960,698; 3,859,197; 3,752,757; 4,194,670; 3,788,966; 3,884,781; 4,137,144; and 3,960,699.
A review of these patents discloses the above described structural elements in various forms, shapes, and connecting means. It will be recalled that the cells are relatively thin and moreover, a significant portion of the center line of each cell is devoted to structurally supporting the transverse membrane and the spaced electrodes. Typically, the central membrane and the two adjacent electrodes comprise three sheet like members positioned across the cell. The three are coextensive with the length and width of the cell. Since adjacent cells are side by side, a common divider plate or wall between two cells will serve for both. This divider plate further restricts the available space to obtain access to the chambers in adjacent cells. The connective areas are relatively narrow so that access to each cell is somewhat limited.
Because of this limitation on the cell width, it is hard to obtain adequate throughput through a limited diameter flow line. The diameter cannot be increased because the diameter is limited by the width of each half of the cell. The cell is enclosed around the periphery by a surrounding closure member, or top and side peripheral flange. If, for instance, the entire cell is 3 inches thick, the separate sides of the cell are approximately 1 inch thick after suitable allowance for the central support frame between the anode and cathode.
The outlet line diameter cannot become very large because it is limited by the width of the space available to complete a pipe connection to the cell to properly plumb the outlet line.
References having a bearing on the present disclosure include U.S. Pat. Nos. 3,930,980 and also 4,033,848. The first reference (column 6, line 41 and following) describes various outlets also set forth in the several drawings of that disclosure. The shape of the opening into the cell is not made clear in that disclosure but there is a transition piece connected to the cell as better shown in FIGS. 9 and 10 thereof. In the other reference, column 4, line 26 discusses a flattened orifice 26 which evenly disperses fluid input to the electrode. These two disclosures are relatively incomplete in terms of setting forth a suitable structure.
The present apparatus sets forth a construction of a cell gas effluent piping or plumbing system which cooperates with an outboard header to remove gas from the cell. Gas and liquid removal is accomplished with minimum back pressure. Moreover, increased removal enables an adequate flow volume to be delivered from each cell into a collection header for several cells, taking into account that they are assembled closely together.
The present apparatus has the advantage of a structure which handles the gasses and liquids to be discharged in an adequate fashion. More than adequate, the output system operates with a minimum of back pressure to collect the gasses from several adjacent cells. Since there are two types of gasses and two effluents formed, there are duplicate header lines which are deployed for connection to alternating cell chambers.
While the foregoing touches briefly on the disclosed apparatus, the scope is determined by the claims which are affixed below following a discussion of the preferred embodiment.